Such a magnetic recording tape cartridge is known as a video tape cartridge for use in recording and/or reproducing video signals in a magnetic recording tape, and such video tape cartridges comprise a pair of reels for winding the recording tape, the reels being driven by driving shafts of a recording/reproducing apparatus, a tape reel locking mechanism for preventing rotation of the reels to keep the intermediate portion of the recording tape, which extends along the front face of the cartridge, stretched when the cartridge is not used and a rotatable lid member mounted on the front side of the cartridge to close the front face thereof to protect the intermediate portion of the recording tape existing along the front face. Furthermore, the recording tape cartridges are provided with a mechanism for releasing the reel locking mechanism when in use and a mechanism either for locking the lid member in the closed position or for releasing the lid member to allow to open the front face of the cartridge when in use.
Conventional video tape cartridges, however, have various drawbacks as hereinafter explained which become remarkably apparent upon decreasing the size of the cartridge.
A locking mechanism for the rotatable lid member for the case of a conventional magnetic recording tape cartridge will hereinafter be described with reference to FIGS. 1 and 2.
The cartridge case 201 comprises a top section 202 and a bottom section 203, and contains therein a magnetic recording tape 204 and a pair of reels (not shown) for winding the magnetic recording tape 204. The cartridge case 201 has an opening 205 in its front surface for drawing the magnetic recording tape 204 out from the case 201 when the record in the magnetic recording tape 204 is to be reproduced so that a portion of the magnetic recording tape 204 is continuously exposed outwardly along the front surface of the cartridge case 201. A rotatable lid member 206 is rotatably supported on the front side of the cartridge case 201 to protect the magnetic recording tape 204 from dust and contact with the hands of an operator.
The rotatable lid member 206 has a front plate 207 for covering the front side of the cartridge case 201, a pair of side plates 208A and 208B provided on both sides of the front plate 207 and a pair of pivotal pins 209 inwardly projecting from the inner surfaces of the side plates 208A and 208B respectively. When the magnetic recording tape cartridge is not in use, the rotatable lid member 206 is in a closed condition to cover the magnetic recording tape 204 exposed along the front surface of the cartridge case 201. In this case, the rotatable lid member 206 is kept closed by a lock means as hereinafter described. When the magnetic recording tape cartridge is mounted in a recording/reproducing apparatus, locking of the rotatable lid member 206 is released by a release member (not shown) of the recording/reproducing apparatus so that the rotatable lid member 206 is rotated to place the magnetic recording tape cartridge in a condition capable of reproducing the record therein.
In the corner of the front surface of the bottom section 203, there is provided a chamber 210 within which a lock plate (not shown) is pivotally contained to be rotatable along a direction perpendicular to the direction of rotation of the rotatable lid member 206. In the side surface of the lock plate, there are provided first and second projections 211 and 212 at a predetermined space to project outwardly through a side wall 213 of the bottom section 203, and the lock plate is elastically pressed against the side wall 213 of the bottom section 203 by a spring member (not shown). In the side plate 208A of the rotatable lid member 206 opposite to the chamber 210, there is provided a recess 214 for engagement with the first projection 211 of the lock plate.
When the rotatable lid member 206, in an opened condition as shown in FIG. 44, is to be closed, an end 215 of the side plate 208A of the rotatable lid member 206 comes in contact with the first projection 211 extending beyond the side wall 213 of the bottom section 203. Since the inner surface of the end 215 is tapered, the end 215 passes over the first projection 211 to press the same so that the lock plate is rotated toward the interior of the cartridge case 201 against the elasticity of the spring member. And when the rotatable lid member 206 is further rotated, the free end of the first projection 211 is engaged in the recess 214 of the side plate 208A so that the rotatable lid member 206 is locked in a closed condition by engagement with the lock plate. In this condition, as shown in FIG. 2, the second projection 212 extends outwardly beyond the side wall 213 to be exposed between the end 215 of the side plate 208A and a stepped portion 216 of the side wall 213 of the bottom section 203.
When the magnetic recording tape cartridge is mounted in a recording/reproducing apparatus with the rotatable lid member 206 kept in a closed condition, the second projection 212 of the lock plate is pressed by a locking release member in the recording/reproducing apparatus inwardly into the cartridge case 201. By virtue of this, the lock plate is rotated against the elasticity of the spring member so that the first projection 211 is disengaged from the recess 14 to release engagement of the rotatable lid member 206 and the lock plate. Then the magnetic recording tape cartridge is lowered within the recording/reproducing apparatus so that an end of the rotatable lid member 206 is caught by a lid opening member (not shown) provided in the recording/reproducing apparatus to be rotated and opened with the lowering of the magnetic recording tape cartridge, thereby exposing the magnetic recording tape 204 as shown in FIG. 1.
As hereinabove described, the conventional magnetic recording tape cartridge is provided in its cartridge case 201 with the chamber 210 exclusively containing the lock plate requiring a wide space for rotation of the lock plate and accommodation of the spring member, and the chamber 210 inevitably occupies a large space. There are further required spaces for extending the second projection 212 between the end 215 of the rotatable lid member 206 and the stepped portion 216 of the bottom section 203 and for inserting the locking release member with respect to the second projection 212. Such requirements in space hinder the reduction in size of the magnetic recording tape cartridge, and further, location of the lock means is limited to the corner of the front surface of the bottom section 203, leading to insufficiency of tolerance in design.
Since, in addition, the rotatable lid member 206 is locked at one end at the side plate 208A, the other side plate 208B tends to be slightly opened by deformation of the rotatable lid member 206 upon receipt of external force for opening the rotatable lid member 206 thereby reducing the function of the rotatable lid member 206.
There is another type of a conventional magnetic recording tape cartridge which has a recess for receiving a locking release member in the lower end of the front plate of the rotatable lid member and a locking release lever provided in the cartridge case in a portion opposite to a recess differing from the lock means as shown in FIGS. 1 and 2. The locking release member is inserted into the recess so as to press a tapered forward end of the locking release lever so that the locking release lever in engagement with the rotatable lid member is rotated to be disengaged from the same.
In this type of magnetic recording tape cartridge, however, the lower end of the magnetic recording tape exposed along the front surface of the cartridge case is apt to be damaged by the locking release member inserted through the recess. For preventing such damage of the magnetic recording tape, it is necessary to separate the insertion path of the locking release member from the magnetic recording tape at a certain space, leading to difficulty in reducing the size of the magnetic recording tape cartridge and insufficiency of tolerance in design.
An example of a conventional locking mechanism of the tape reel is now described with reference to FIG. 3. The mechanism is provided in the vicinity of a rear wall 302 of a bottom section 203 of the cartridge case, and comprises a through-hole 303 for receiving a release pin (not shown), a pawl member rotation lever 304, two pawl members 305 and two coiled springs 306. The through-hole 303 is formed in a substantially central portion of the bottom section 203 in the vicinity of the rear wall 302, and is exclusively used for receiving the release pin (not shown). The lever 304 comprises a block member 307 for closing an upper open end of the through-hole 303, a column 308 connected with the bottom of the block member 307 and a pair of pressing portions 309 extending from the columns 308 substantially perpendicularly with respect to the block member 307. The lever 304 is rotatably carried on a pair of projections 310 extending from the rear wall 302 toward the through-hole 303. Each of the pawl members 305 comprises a cylindrical body 312 rotatably engaged with the outer periphery of a shaft 311 projectingly formed in the bottom section 203, an arm 313 being in contact with the pressing portion 309 of the lever 304 and a pawl 315 extending toward a reel 314. The shaft 311 is engaged in its upper end with a coiled spring 306 which has an end being in contact with a contact pin 316 projecting from the bottom section 203 and another end being in contact with the pawl 315 of the pawl member 305. By virtue of the elasticity of the coiled spring 306, the pawl 315 and the block member 307 of the pawl member 305 are respectively pressed against the reel 314 and to close the through-hole 303. A plurality of grooves 318 are formed in the outer periphery of a flange 317 of the reel 314 so that rotation of the reel 314 is stopped by the forward end of the pawl 315 engagingly entering the groove 318.
When this type of magnetic recording tape cartridge is mounted in a recording/reproducing apparatus, the magnetic recording tape cartridge is lowered with respect to the recording/reproducing apparatus so that two standard pins (not shown) provided in the recording/reproducing apparatus are inserted into a pair of through-holes 319 formed in the front surface of the bottom section 203 of the magnetic recording tape cartridge for location of the same. A rotation stoppage release pin (not shown) provided in the recording/reproducing apparatus is inserted into the through-hole 303 so that the block member 307 is raised against elasticity of the coiled spring 306. By virtue of this, the pressing portion 309 of the pawl member rotation lever 304 falls toward the rear wall 302 thereby rotating the pawl member 305 about the shaft 311 so that the pawl 315 is disengaged from the groove 318 to allow rotation of the reel 314.
In this type of conventional magnetic recording tape cartridge, however, the bottom section 203 requires a large space for providing the through-hole 303 for receiving the release pin and the through-holes 319 for receiving standard pins which are formed individually, leading to difficulty in reducing in size the magnetic recording tape cartridge. Further, the parts of the conventional locking mechanism for stopping the tape reel are complicated in shape and construction, requiring complex mold designs and steps for assembling each of the components.